The disclosure of Peters U.S. Pat. No. 6,283,230 entitled METHOD AND APPARATUS FOR LATERAL WELL DRILLING UTILIZING A ROTATING NOZZLE, issued Sep. 4, 2001, as well as the disclosures of my co-pending U.S. patent application Ser. No. 12/350,707, and U.S. Provisional Patent Application Ser. Nos. 61/044,552 and 61/044,639, filed Apr. 14, 2008, are hereby incorporated herein by reference in their entireties.
A large number of wells have been drilled into earth strata for the extraction of oil, gas, and other material therefrom. In many cases, such wells are found to be initially unproductive, or decrease in productivity over time, even though it is believed that the surrounding strata still contains extractable oil, gas or other material. Such wells are typically vertically extending holes including a casing usually of mild steel pipe having an inner diameter of from just a few inches to about eight (8) inches or more in diameter for the transportation of the oil, gas or other material upwardly to the earth's surface.
In an attempt to obtain production from unproductive wells and increase production in under producing wells, as well as for improving production from wells generally, methods and apparatus for cutting a hole in the well casing and forming a lateral passage therefrom into the surrounding earth strata are known. Reference for instance, my previous Peters U.S. Pat. No. 6,283,230, which utilizes a down hole unit including a casing cutter in a first step for cutting the hole in the casing, and a flexible tube carrying a nozzle through which fluid is discharged for drilling the lateral passage as a second step. Both are advanced laterally from down hole apparatus, e.g., a kick-off shoe unit supported in the well by a rigid tube, the casing cutter being advanced against the casing, and the flexible tube and nozzle through the hole through the casing and into the lateral passage as the passage is increased in length.
The kick-off shoe unit has an internal passage or elbow connecting with a laterally facing opening through which the casing cutter and flexible tube extends during the casing cutting and lateral passage forming operations, respectively. The casing cutter is attached to the end of a string or series of universal joints, or other flexible device, configured and suspended from a rotatable output shaft of a motor, so as to be received through an upper opening of the elbow of the shoe and so as extend through the elbow of the shoe to the inner surface of the casing. A tubular sheath is suspended from the output shaft and contains and protects the cutter and universal joints during the descent through the tubing down to the kick-off shoe.
The motor is suspended from flexible tubing within the larger diameter rigid outer tube, and is lowered through the outer tube until the cutter contacts the inner surface of the casing, causing the flexible tubing to slacken, which signals to the operator that the cutter is in the cutting position in contact with the casing. The operator will then adjust the tension in the flexible tubing to hold the cutter against the casing with a sufficient force to cut through the casing. Here, it has been found that the flexible tubing will have a significant amount of resilience or elasticity which can amount to as much as several feet of stretch due to the long length thereof, which can vary from as little as a few hundred feet to as much as several thousand feet depending on the depth of the well, which makes it difficult to accurately gauge the contact force between the cutter and the side of the casing. As a result, typically, when the operator determines that the cutter is properly positioned and the desired cutting force is present, the motor will be operated for a period of time estimated to be adequate for fully penetrating the casing. The cutter is then retrieved and examined for characteristics, e.g., worn consumable shim, indicative of full penetration of the casing.
As the casing cutter is cutting the casing, it has been found that no direct feedback is provided to the operator at the surface of the well. As the cutter advances, there is not a perceptible change at the top of the well, in the position of the tubing supporting the cutting apparatus, as a result generally of the above noted elasticity of the suspended apparatus. Typically also, the portion of the weight of the suspended flexible tubing, motor, and drilling apparatus, not supported from above provides the cutting force, which force can thus vary widely as a function of operator experience, and the depth of the well and length of tubing required, which can be a shortcoming in the use of this apparatus.
Accordingly, what is sought is a solution to the above shortcoming, by providing a more uniform and predictable cutting force.